I'd think so, because why would they offer all the gym equipment? :/
I have a chubby kid that gets energized and does all these push ups and sit ups but she's still chubby. So I guess kids can't lose the pounds.
Maybe teens and up can though...

@Laspyra same here! My sim kept gaining weight, even only eating when she was hungry. It turns out, for The Sims 4 regular workouts are key! I had my sim do a full workout on the treadmill every day for about a sim week, and she was back to her starting size in no time! Its kind of a drag though
(And I agree, gardening is a workout in itself!)